package org.apache.lucene.analysis.standard;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.analysis.*;

/** Normalizes tokens extracted with {@link StandardTokenizer}. */

public final class StandardFilter extends TokenFilter implements StandardTokenizerConstants {

    /** Construct filtering <i>in</i>. */
    public StandardFilter(TokenStream in) {
        super(in);
    }

    private static final String APOSTROPHE_TYPE = tokenImage[APOSTROPHE];
    private static final String ACRONYM_TYPE = tokenImage[ACRONYM];

    /** Returns the next token in the stream, or null at EOS.
     * <p>Removes <tt>'s</tt> from the end of words.
     * <p>Removes dots from acronyms.
     */
    public final org.apache.lucene.analysis.Token next() throws java.io.IOException {
        org.apache.lucene.analysis.Token t = input.next();

        if (t == null)
            return null;

        String text = t.termText();
        String type = t.type();

        if (type == APOSTROPHE_TYPE && // remove 's
                        (text.endsWith("'s") || text.endsWith("'S"))) {
            return new org.apache.lucene.analysis.Token(text.substring(0, text.length() - 2), t.startOffset(), t.endOffset(), type);

        } else if (type == ACRONYM_TYPE) { // remove dots
            StringBuffer trimmed = new StringBuffer();
            for (int i = 0; i < text.length(); i++) {
                char c = text.charAt(i);
                if (c != '.')
                    trimmed.append(c);
            }
            return new org.apache.lucene.analysis.Token(trimmed.toString(), t.startOffset(), t.endOffset(), type);

        } else {
            return t;
        }
    }
}
